1. Field of the Invention
The present invention relates to wire rope and, more particularly, to wire rope embodying a lubricant, and methods for producing the same.
2. Description of the Prior Art
Wire rope incorporating lubrication, principally heavy viscous lubricants such as petrolatum, is known in the art, and lubricated wire rope has further been impregnated with and surrounded by a jacket of a thermoplastic material in order to protect the wire strands and encapsulate the lubricant. The lubricant is generally extruded into the interstices of the wire strands, while the plastic surrounds either the strands individually or is extruded into the interstices of the wire rope.
Wire rope is formed by twisting together multiple wire strands around a central core. The strands are in turn formed by twisting together wires, also around a core material which may be wire, fiber or the like. The core strand likewise may be fiber, twisted wire or a combination thereof. In the formation of the strands, a heavy viscous lubricant may be incorporated within the interstices formed by the twisted wires and strands. Various configurations of wires and strands have been developed, depending upon the properties and characteristics desired in the wire rope. In the manufacture of wire rope, the strands are twisted together to form the rope by means of what is commonly termed a closing die. The heavy viscous lubricant is conventionally incorporated into the wire rope and strands by an injection mechanism adjacent the closing die. Where the rope or portions thereof are to be encapsulated in plastic, appropriate extrusion dies are utilized.
The construction of wire ropes and the incorporation therein of heavy viscous lubricants and surrounding thermoplastic materials and sheaths are disclosed in U.S. Pat. No. 3,195,299, issued July 20, 1965, to A. Dietz, for WIRE ROPE; U.S. Pat. No. 3,318,082, issued May 9, 1967, to P. P. Riggs, for PLASTICS IMPREGNATED ROPE; U.S. Pat. No. 3,824,777, issued July 23, 1974, to P. P. Riggs, for LUBRICATED PLASTIC IMPREGNATED WIRE ROPE; U.S. Pat. No. 3,874,158, issued Apr. 1, 1975, to F. Chiappetta et al., for WIRE ROPE WITH PLASTIC IMPREGNATED LUBRICATED CORE; and U.S. Pat. No. 4,120,145, issued Oct. 17, 1978, to F. Chiappetta et al., for LUBRICATED PLASTIC IMPREGNATED WIRE ROPE. Where necessary for a more detailed understanding of the present invention, the disclosures of the foregoing patents are incorporated herein by reference.
Oil bearing polymeric lubricating compositions have been disclosed which contain a hydrocarbon oil impregnated or encapsulated in the interstices of a high molecular weight polymer, such as polyethylene, to provide a gel like lubricating composition. Such materials are sometimes referred to as a microporous polymer lubricant or as a polymeric lubricating medium. See, for example, U.S. Pat. No. 3,541,011, issued Nov. 17, 1970, to W. J. Davis et al., for LUBRICATING COMPOSITION; and U.S. Pat. No. 3,547,819, issued Dec. 15, 1970 to W. J. Davis et al., for LUBRICATING COMPOSITION. These and similar lubricant materials may be formed by mixing polymeric materials, such as polyethylene, polypropylene, polyurethane, polyesters and polyamides with an appropriate lubricating oil, such as hydrocarbon or petroleum oils, silicone oils or other liquid lubricating materials. In use, the polymeric lubricating medium wicks lubricating oil to surrounding adjacent surfaces or areas. An increase in pressure increases the amount of oil wicked or weeped from the composition, and the composition reabsorbs oil when the pressure is released. Polymeric lubricating compositions other than those described in the patents to Davis et al. may be utilized to advantage.